416 



CRUSTACEA. 



The scvciitli ami last section, the Nototoda, is formed of Crahs having the four or two posterior 

 ]oi;-s iu^rrtoil .a1)ovo the {ihine of the others, and :seeiiiiiig to lie durbal, and din-cted upwards. In tlio^e 

 wliere tliev are not terminated iiy a sharj) hook, the animal generally u^es tliem to retain in its hohl 

 various marine productions, such as tlie valves of shells, sea-weeds, &c., witli which it covers itself. 

 The tail has se.'eu joints in both sexes; the majority have the abdomen bent beneath the breast, and 

 the legs termiuated by a short hook, and unfitted for swimming. 



Hoinoluy Leacb, have the carapax nearly square ; the antennae lon^ ; the ocular piMlunciu.s lonj;- ; the claws of 

 the males larger than the females, and the posterior pair of legs directed upwards. The outer foot-jaws ai-e tun^ 

 and exposed [as in W\e Macrara]. The ty\te, Ji. sp)Hi/ro)iSy Leach, is a native of the Mediterranean, and is the 

 U-ppocardnua of Ajdrovandus. 



JJorippCf Fab., has the four hind-le^,^s elG\":itcil, as has also Drowln, F:ili. 



Di/nomenc, Latr., has the carapax of the ordinary form, and the two hind 1p2:s alone elevated. 



Raiiijin, Laui., is a sin:,'"ular s'enus, difl'erin;^; from all other Brachyura in having; the abdomen extended, [Ijut 

 not furnished at the end willi an apparatus for swiinininir] ; and from the other yolopoihi^ in haviriL^'' tlie six 

 intermediate le,G;"s dilated ;uid natatorial. TIil- carapax is of a reversed trian;2;ular forn), tlie fiont nmcli toothed. 

 The species are exotic. 



[The Dravhijiirons Crustacea, here given as a single genus, Cancer, have, ffora the great nnmlier oi 

 species of w Inch they consist, tbeir large size, and facility of preservation, owing to their solid envelopes, 

 attracted the attention of many recent authors. The Malacostraca Podopthalma Britannica, of 

 Leaeli ; the Ilistnire Naturelle des Crustaces, by Milne Edwards; the Fauna Japonica, of De Ilaan ; 

 the Mrnioirs of Professor Bell, pubhshed in the Transactions of the Zoological Society, and by 

 .Mr. MucLeay, in 1 »r. Smith's Illustrations of Southern Africa ; together with Polydore Koux's elegant 

 work upon the Crustacea of the Mcihtei'vancan, must be consulted l.iy those who would desire to 

 become acquainted witli the i^ingulur forms aud nudtitudinous genera established in this tribe of 

 animals.] 



THE SECOND FAMILY OF BECAPODA,— 



Di'CAPODA Macrura [Exochriala, Fabricias), — ■ 



Is distinguished by having, at the extremity of the tail, on each side, appendages*, ordinarily forming a 



swimmeret or inslnnnent for swimming, tlie tail itself being at least as huig as the liody, extended, 



e\[)Osed, and bent nuih;r fmly towards the ])i)sterior cxtreuiity. Its, under-.:iLdc generally presents, in 



lioth sexes, five pairs of false feet, each terminating in two 



plates or filaments. The tail is always comjioscd of seven 



segments. The bvanchi;e are formed of vesicular, bearded 



and villose pyramids, arranged, in many, either in two row"s 



or in separate bundles. Tlic antennas are generally long and 



exserted ; the ocular peduncles are mostly short. The rxtmial 



foot-jaws are generally narrow, long, and palpifoiin, and do 



not entirely hide the other [internal] parts of the mouth. 



gate than in the Brachyura, and ordinarily terminated in front in a puiut. ?-lM. .Vuilmiin and 



i\lilne Edwards (to wbnm we must refer fur ])articnhtrs) have noticed that in the lobster (Astaci's 



'i;iar/nns-, Fait.), in addition to the two large lateral vcn'Hu canals, there exists a ihird, loilgeil in the 



sternal cavity, in which respect the venous systems of the Macrura and Stoniapoda agree. The ]\ia- 



enn-a never [or but in a very few instances] quit the water, and w"ith a very few exceptions they are 



all marine. 



Aihipting the plan of Delper and Gronovius, tlie Macrura may be considered as forming but a single 

 gennsf, Astaens, which may be thus divided : — 



The carapax is narrow and more elon- 



• Tl[(?se ftp[n;iHlnj;(?M nrc comp'tsed of Ibrce piL'Ucs, naniLly, ii liiise, 

 (nr support U; ilie tnu otlnTs) , firticril;Uiiij; with [lie peiiultlmntc- auy- 

 nieiil i the tcruiiiml sc|,'ment generaUy forming witli tlii'm a fiiri-tike 

 swimnieret ; liut in tlie tKrmlniLl speciea tliK appcmlft^fes are replaced 

 liy fiintncntB. The Kub-ftlitlominiil false leg^s are formed on the aiiiiie 

 Tii'iilel, and vary in numltcr, there belnj[ only three or four small 

 pdirt, In the Anoin»lri, ;uid wanting in the nmlea (except the anterior 

 [lairl. In the Hermit Crahs they seem to fxist unlv fm nni; side. But 



in Lhe sulisi.'i-iuciit suh^'ciicra tlicy are constnntly laruer, luid tlierL' nre 

 ljv{' pairt,, supjjiirtirji; Uie ci;j-i,rs and being useful in s«inim;iig. In Uie 

 sectiuii Anomaln, the peduncle of the intermediate mitenna is prn- 

 pnrtionably loiifrer, and the two or four posterior feet snidller, thus 

 upproaehiny; the Brnchyuni. 



t The sections whieli mx have proposed ought rather to f'Tin -o 

 raajiy ({eiiera, based upon those of yubriems. 



